Display screen or portion thereof with transitional graphical user interface



FIG. 1 is a front view of a display screen or portion thereof with transitional graphical user interface, showing a first image in a sequence, showing our new design;

FIG. 2 is a front view showing a second image thereof;

FIG. 3 is a front view showing a third image thereof;

FIG. 4 is a front view showing a fourth image thereof;

FIG. 5 is a front view showing a fifth image thereof;

FIG. 6 is a front view showing a sixth image thereof; and,

FIG. 7 is a front view showing a seventh image thereof.

The outermost broken lines illustrating portions of a display screen or portion thereof form no part of the claimed design. The remainder of the broken lines illustrating portions of the graphical user interface forms no part of the claimed design.

The white circle portion bounded by solid lines in the tonally-shaded rounded rectangle forms a part of the claimed design.

The white circle portions bounded by broken lines in the tonally-shaded rounded rectangle form no part of the claimed design.

The contrast shown in grayscale in the figures represents a contrast of appearance.

The appearance of the transitional image sequentially transitions between the images shown in FIGS. 1-7. The process or period in which one image transitions to another image forms no part of the claimed design. 

CLAIM The ornamental design for a display screen or portion thereof with transitional graphical user interface, as shown and described. 